Methodology Development for Tumble Port Evaluation

The objective of this work was to develop a methodology to rapidly assess comparative intake port designs for their capability to produce tumble flow in spark-ignition engine combustion chambers. Tumble characteristics are of relatively recent interest, and are generated by a combination of intake port geometry, valve lift schedule, and piston motion. While simple approaches to characterize tumble from steady-state cylinder head flow benches have often been used, the ability to correlate the results to operating engines is limited. The only available methods that take into account both piston motion and valve lift are detailed computational fluid dynamic (CFD) analysis, or optical measurements of flow velocity. These approaches are too resource intensive for rapid comparative assessment of multiple port designs. Based on the best features of current steady-flow testing, a simplified computational approach was identified to take into account the important effects of the moving piston. The method was compared to moving-piston CFD analysis, and after some refinement the ability to meet the project objective was achieved. The method was found to consistently rank the tumble performance of comparative port designs, and lead to the same conclusions as predicted with moving-piston CFD modeling. Total resource requirements were found to be less than one third that of the moving-piston analysis for the same engine. Example applications to various engines are presented.